Barely five months later, they found a "10/10" match in Michael Menafee, a Chicago native who was registered to the DKMS national bone marrow registry in the U.S.

After Menafee underwent the hour-long procedure and hip extraction required for donation at Georgetown University in Washington, D.C., Jaxson successfully received the stem cells and spent eight weeks at Sick Kids Hospital in Toronto. According to his mother, he was "not allowed to leave his room at all" for half of that time.

Jaxson Slade in 2013. (Handout)

"I can't tell you how many days and nights that I wished I could trade places with him so he wouldn't have to feel pain," says Melissa Slade, Jaxson's mother, in a statement to The Huffington Post Canada.

She adds that what made the transplant even more difficult for her and their family was juggling Jaxson's care with that of his older brother Morgan, who was three at the time. Her husband Curtis Slade took off eight months of work to spend more time with his son as he recovered, too.

Jaxson Slade in 2017. (Handout)

Jaxson's since had a smooth recovery, as has Menafee, who is now 32, and based in Guatemala with the Peace Corps.

"I was thankful and excited to hear how great Jaxson was doing," writes Menafee in an email to The Huffington Post Canada. "It took me [about a week and a half] to get back to normal. The pain was minimal, it was as if I just fell down on a patch of ice."

"We were a perfect match, which was incredible to me."

This unlikely match also caught DKMS CEO Carina Ortel by surprise, as Jaxson is Caucasian and Menafee is African-American.

"Finding the perfect match from somebody from a different ethnicity is very rare and truly a miracle."

"Finding the perfect match from somebody from a different ethnicity is very rare and truly a miracle, but it does happen," says Ortel over the phone. "But because chances are much higher on finding a match within an ethnicity, we do make more of an effort to register diverse donors in the registry, as only six per cent are African-American, and one of them is Michael [Menafee]."

Jaxson and Menafee may be a genetic odd couple, but they've subsequently formed quite a bond.

The four-year-old and his American bone marrow donor met for the first time this month — almost three years after their procedure connected them to each other — to spend the Easter holiday together.

Michael Menafee and Jaxson Slade meet for the first time in Paradise, N.L. (Handout)

Menafee calls the heartfelt reunion in Paradise, N.L. "an intangible moment," and brought Slade a Mario book bag, which he reportedly "loved" and now "he brings it everywhere he goes."

"I was and am happy he is a healthy, nearly five-year-old full of energy and life," says Menafee. "Jaxson knows that I helped him when he was ill. Since he is so young, he does not understand how gravely ill he was, [but] someday he will understand more."

Jaxson Slade, Curtis Slade, Michael Menafee, Morgan Slade and Melissa Slade all sit together after meeting for the first time. (Handout)

The Slades first reached out to the donor last April, first through email and then via Facebook. Menafee says they now speak about once a week.

He flew out to Newfoundland about a year later, and the family hosted an open house to celebrate his arrival. The Slades also travelled with Menafee to visit local historic sites in the area like Signal Hill and the Battery.

"It was an emotional and thankful experience for all who attended," says Menafee. "I like it here a lot! The people are friendly and [Newfoundland] has a lot of rich history."

Though Menafee's week in Paradise, N.L. has come to a close, he hopes he and the Slades will continue to keep in touch.

"I absolutely will return to visit Jaxson and the rest of the family," says Menafee. "They all are a part of my family now and mean a lot to me."